This disclosure relates to a reduced graphene oxide doped with a dopant. It also relates to a thin layer and a transparent electrode that includes the reduced graphene oxide.
Generally, graphite is a stack of two-dimensional graphene sheets formed from a planar array of carbon atoms bonded into hexagonal structures. Single or multiple-layered graphene sheets display advantageous properties. The most advantageous of these properties is that electrons flow in an entirely unhindered fashion in a graphene sheet. As a result, the electrons flow at the velocity of light in a vacuum. In addition, an unusual half-integer quantum Hall effect for both electrons and holes are observed in graphene sheets.
The electron mobility of graphene sheets is about 20,000 to 50,000 cm2/Vs. Also, it is preferable to manufacture products using graphene sheets rather than carbon nanotubes, since products made from graphite are inexpensive while products made from carbon nanotubes which are used in applications similar to those in which graphene sheets are used, are expensive due to low yields during synthesis and purification processes even though the carbon nanotubes themselves are inexpensive. Single wall carbon nanotubes exhibit different metallic and semiconducting characteristics according to their chirality and diameter. Furthermore, single wall carbon nanotubes having identical semiconducting characteristics have different energy band gaps depending on their chirality and diameter. Thus, in order to obtain a metallic single wall carbon nanotube composition or a semiconducting single wall carbon nanotube composition, it is desirable to separate the single wall carbon nanotubes from each other in order to obtain desired metallic or semiconducting characteristics respectively. However, separating single wall carbon nanotubes is not a simple or inexpensive process.
On the other hand, it is advantageous to use graphene sheets since it is possible to design a device to exhibit desired electrical characteristics by arranging the graphene sheets so that their crystalline orientation is in a desired direction since their electrical properties vary with crystalline orientation. It is envisioned that these characteristics of graphene sheets will render them useful in carbonaceous electrical devices or carbonaceous electromagnetic devices in the future.
However, although graphene sheets have these advantageous characteristics, a process of economically and reproducibly preparing a large-sized graphene sheet has not yet been developed. Graphene sheets can be prepared using a micromechanical method or a SiC thermal decomposition method. According to the micromechanical method, a graphene sheet separated from graphite can be deposited on the surface of Scotch™ tape by attaching the tape to a graphite sample and detaching the tape. In this case, the separated graphene sheet does not include a uniform number of layers, and the graphene sheets do not have a uniform shape. Furthermore, a large-sized graphene sheet cannot be prepared using the micromechanical method. Meanwhile, in SiC thermal decomposition, a single crystal SiC is heated to remove Si by decomposition of the SiC on the surface thereof, and then residual carbon C forms a graphene sheet. However, single crystal SiC is very expensive, and a large-sized graphene sheet cannot be easily prepared.
Meanwhile, an attempt has recently been made to prepare graphene using a chemical process. The graphene is separated from graphite by treating graphite with a chemical substance. However, the process is not completely controllable. Another attempt is to form and disperse graphene oxide. Since graphene oxide is easily dispersed, a thin layer made of the graphene oxide can easily formed. Another method of manufacturing graphene is to use reduced graphene oxides. However, neither of these attempts reproduce the electrical properties of graphene. Recently, a graphene thin layer has been formed by mixing a graphene oxide and a silica substance, but this graphene thin layer does not have excellent properties either.